First stage forced circulation in boilers



Dec. 23, 1958 REHM 2,865,343

FIRST STAGE FORCED CIRCULATION IN BOILERS Filed Dec. 20, 1954 2 Sheets-Sheet 1 INVENTOR. 6x550?) fife/"(m BY PARKER 8- CARTER ATTORNEYS G. A. REHM Dec. 23, 1958 2 Sheets-Sheet 2 Filed Dec.

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FIRST STAGE FORCED CIRCULATION IN BOILERS Application December 20, 1954, Serial No. 476,195

Claims. (Cl. 122406) This invention resides in the field of steam boilers and boilers generally and is an improved structure for gencrating both hot water and steam.

A primary object of my invention is a new and improved boiler structure having means to prevent the water wall tubes around the furnace space from being damaged when the power fails.

Another object is a boiler structure with a first stage forced circulation and having a safety connection between the first and second stages.

Another object is a boiler of the above type constructed and arranged to be fired by a stoker.

Another object is a boiler of the above type with a steam and hot water drum having means for condensing and breaking up any large steam bubbles from the water wall tubes.

Another object is a stoker-fired boiler having a steamcondensing cold water spray across the intake to the hot water outlet connection of the upper drum.

Another object is aboiler unit having a housing with its space divided laterally into a forward combustion space and a rearward gas path with its upper drum divided gen erally in the same relation or proportion.

Other objects will appear from time to time in the ensuing specification and drawings, in which:

Fig. l is a sectional view taken longitudinally through my new and improved boiler structure; and

Fig. 2 is a double section, the left half being taken along line A-A in Fig. 1 and the right half being taken along line 3-8 in Fig. l.

l have shown a boiler which is provided with a housing having a front wall 1d and a back or rear wall 125 closed on each side by suitable side walls 14 and 16. The floor level surrounding this installation is indicated generally at 18, and any suitable foundation or supporting base is The top of the boiler is closed by a suitable roof or upper wall 22. A lower wall or 9 United States Patent floor 24 rests on the foundation and closes the bottom of the housing, while an intermediate wall 26 extending laterally across the boiler projects upwardly and terminating at 28 to divide the boiler housing generally intov a forward combustion or furnace space 30 and a rearward gas path 32 leading to suitable outlets 34 shown in dotted lines in Fig. 2. The side walls, front and rear walls, as well as the fioor and top of the housing, may be formed of steel plate or the like and lined with a suitable mineral Wool felt, or any other satisfactory insulation. I

The housing is provided with a boiler unit having a first stage forced circulation system which includes two side wall headers 35 and 38 interconnected across their rear ends by a rear header 40. The front end of the side wall headers are connected by a front header 42 which is positioned above a suitable centrally disposed opening 44 for a stoker 46 having a spreader grate 47. The floor of the housing has an ash hopper 49.

The front header 42 is connected to the ends of the 'side Wall headers by suitable pipes 48 in Fig. 1. Thus, the rear header along with the side headers 36 and 38 and the front header 42, are connected together in a square or rectangular manifold-type header which is supplied with cold water or water coming back from the sys tern by a suitable connection 50 which joins the center of the rear header as at 52. This manifold or rectangular header manifold surrounds the grate and conforms generally to the bottom of the combustion space. The walls of the combustion spaceare lined by water wall tubes 54 which connect to the manifold at theirlower ends and to an upper drum 55 at their upper ends. A

suitable tile plate or slab 56 protects the bottom of the upper drum from the high temperatures developed in the combustion space.

The hot gases from the combustion space pass over the intermediate Wall 26, and a plurality of alternate generally upright baffles 58, 60, and 62 are disposed in the after compartment to provide a tortuous path for the hot gases leading to the outlets 34. An air inlet 64 with a damper 65 is provided in the hopper 49 for connection to a suitable forced-draft fan either on the operating floor of the unit or in the basement, as desired. A connection 66 may be provided in front wall for auxiliary gas or I oil burners, as desired, to augment the stoker.

wall tubes enter the drum in a symmetrical arrangement on both sides. Baffle structures 76 and 77 extend longitudinally along the sides of the drum and project downwardly so as to mask or cover the openings from the water wall tubes. These baffle structures include plate-type elements 78 and 79 which extend below the normal water level, as shown in Fig. 2, and the bottom portion is completed by a screening medium St] on the left side and 82 on the right. In Fig. 2 this longitudinal baffie structure appears on the left side of the upper drum and it will be understood that the opposite side of the drum in the forward portion is symmetrical and is shown broken away in Fig. 1. These longitudinal baffles extend along each side and engage and can be connected to the lateral bathe 68 with the lower screening mediums interconnected so that all of the open steam space above the water line in the drum is completely baffled and communication below the baffles is provided with a screening medium.

Hot water and steam are formed in the water wall tubes which exhaust into the forward portion of the drum. This is masked or baffied by the longitudinal structure.

The baffles deflect the steam and hot water downwardly through the screening medium which breaks up and assists condensation of the large steam bubbles.

The rear portion 72 of the upper drum is provided with a hot water outlet connection 34 which has a pipe extending below the normal water level. Before the hot water and steam in the forward portion 70 of the drum can pass through the outlet, it is deflected downwardly by the bathe 68 through the screening medium 74 which again breaks up any steam bubbles that are left over.

Two lower drums 86 and 88 are longitudinally positioned on each side of the rear part of the housing, and a plurality of natural circulation tubes 90 and 92 extend upwardly from them and enter the rear portion of the upper drum. All of these tubes extend through the gas path as defined by the baffles 58, 60 and 62 so that natural circulation of the hot water in the system will take place between the rear portion of the upper drum and the two lower drums 86 and'88.

each side are connected to the rear header 40 ofthe gas path and enter the rear part of the upper drum at 100. I have shown two such tubes on each side of the unit in Fig. 2, and it should be understood that any suitable number and size of tubes can be used to establish communication between the inlet water manifold and the rear portion of the upper drum. The connection 100 of these auxiliary tubes with the upper drum is generally adjacent the hot water outlet pipe 84, and a baffle plate 102 is positioned between them so that the contents exhausting from the auxiliary tubes is forced to go around and intermingle with the water in the drum before it can be taken out through the outlet.

An. auxiliary steam outlet 104 is provided in the forward portion 70 of the upper drum and the drum has suitable manholes 106 with the usual removable covers. The gas path is provided with suitable accesses for inspection and repair as at108. The lower drums are also provided with suitable manholes 110 and covers.

The use, operation and function of my invention are as follows:

I provide a boiler housing having upper and lower drums interconnected by natural circulation tubes which may be termed the second stage of circulation. The housing space is divided into a forward combustion chamber and a rear gas path by an intermediate wall. The lower portion of the combustion space is surrounded by a header manifold which has a water inlet. A stoker and grate are positioned generally at the fioor level of the combustion space and a hopper is provided below them for ash disposal. Water wall tubes line the combus-.

tion space and are connected to the header manifold and the upper drum forming what may be termed the first stage of circulation. A suitable pump can be connected to the inlet 50 so that the water will be forced through the first stage under pressure.

Two lower drums are provided on each side of the housing along the floor of the gas path and are connected by the natural circulation tubes to the upper drum.

The upper drum is divided by a lateral baffle structure into a forward and rear portion. The water wall tubes surrounding the combustion space communicate with the forward portion, while the natural circulation tubes passing through the gas path communicate with the rear portion. The forward portion of the upper drum has longitudinal baffles which direct the hot water and steam from the water wall tubes downwardly through a longitudinal screening mesh or medium to break up the large steam bubbles and aid in condensation. The lower part of the lateral bathe dividing the upper drum in the forward and rear portions also has a screening medium so that all of the steam will be forced through the screening medium and the steam bubbles will be additionally broken up and condensed. Very little steaming will ,occur in the space above the hot water in the rear portion of the drum, and an auxiliary steam connection is provided in the forward portion of the drum.

One or more suitably sized tubes interconnect the forced circulation system and the natural circulation system. As shown in the drawings these tubes connect the rear header of the water inlet manifold to-the rear portion of the upper drum. The purpose of this is as follows:

A water pump supplies return water through the inlet 50 under'pressure and forces it upwardly under pressure through the water wall tubes into the forward part of the upper drum. The stoker supplies high temperature heat to the combustion space, and'in the event of a power failure which would stopthe pump, all of the water would be heated in the first stage and would be forced into the upper drum. The water wall tubes would burn out very quickly or would be seriously damaged,

and the unit would have to be shut down so that the tubes could be repaired or replaced, involving a con siderable loss. To prevent this, the auxiliary tubes provide a connection between the natural circulation system in the after-part of the boiler housing and the forced circulation system in the forward part so that, when the pressure fails due to a power stoppage, the water in the natural circulation system will flow back into the first stage through the auxiliary pipes or tubes 94 and 96 to the rear header 40 of the manifold and then upwardly again through the water wall tubes. The water passing through the tubes would absorb the heat supplied by the stoker and would prevent the tubes from being damaged or ruined.

These auxiliary tubes interconnecting the natural circulatiou system with the forced circulation system also perform another function. The pump supplying water to the header manifold can be shut down while the stoker is supplying heat to the combustion space. A suitable detergent or cleaning compound can be intro duced into the system at any suitable point so that it will flow through the forced and natural circulation systems. The auxiliary pipes or tubes complete the circuit. The stoker acts as a pump to circulate the cleaning compound from one system to the other and back again through the auxiliary tubes.

With this type of unit a steam space is provided above the normal water level which will take care of any expansion and contraction in the water system. Thus, I do not have to provide any expansion headers or drums either'in the system or beyond it at any point.

While 1 have shown and described a stoker, it should be understood that suitable gas or oil burners can be used as an auxiliary source of heat, as at 66 in Fig. l, or can be used without the stoker. Accordingly the invention should be considered as utilizing either solid, liquid or gaseous fuels, although, of course, the housing structure is specifically arranged to accommodate a stoker and its grate and hopper.

Hot water is taken out of the upper drum through the outlet 84, and it should be noted that under normal firing relatively cold water will be taken from the rear header 40 of the header manifold through the auxiliary tubes and admitted into the rear portion of the upper drum. This relatively cold water intermixes with the hot water directly adjacent the hot water outlet 84, to additionally condense any undesirable steam bubbles. To prevent the cold water from flowing directly into the hot water outlet 84, I have provided a bafile in the lower portion, as at W2, which forces the cold water stream to thoroughly intermix with the hot water and steam because it has to fiow over the top of the bafiie. This completes the condensation of the steam carried by the hot water, as well as preventing the cold water from being taken directly up through the outlet 84.

The steam can be withdrawn through the auxiliary outlet 104 and the hot water through the outlet 84 to suitable points of use, such as for heating, cooking and the like, and it can be returned to the boiler through the inlet 50. The water return to the waterwalls and boiler is through the inlet 50 by pump pressure. Water circulation under normal operation through the water wall tubes enclosing the furnace is forced circulation by reason of this pump pressure.

The unit can be provided with the usual accessories and attachments, such as soot blowers, air preheaters, feed water controls, and the like; however these form no part of the present invention and have not been shown or described.

While I have shown and described a preferred form of my invention, it should be understood that numerous modifications, substitutions, alterations and changes can be made without departing from the inventions fundamental theme. I therefore wish that my invention be unrestricted except as by the appended claims.

I claim:

1. In a boiler assembly, a housing, a boiler structure including an upper drum disposed generally in the top center of the housing, the housing being divided generally into a forward furnace space and a rear gas path, the for ward space having a forced circulation system including a generally rectangular manifold and a plurality of water wall tubes lining the forward space connected between the manifold and the upper drum, a cold water inlet for the manifold adapted to be connected to a pump, a natural circulation system in the rear gas path including a pair of lower drums generally parallel to the upper drum and disposed on opposite sides of the housing, a plurality of convection tubes between the upper and lower drums, a fuel supply for the furnace space, and a transverse baffle structure in the upper drum dividing it into portions that conform generally to the division of the housing to divide the upper drum between the forced and natural circulation systems, the baffle structure including a screening medium below the normal water level to allow hot water to flow through the forward portion into the rear portion.

2.- The structure of claim 1 characterized by and including a hot water outlet in the rear portion of the upper drum and an auxiliary steam outlet in the forward portion.

3. The structure of claim 1 characterized by and including an auxiliary connection between the cold water inlet and the natural circulation system.

4. The structure of claim 1 further characterized by and including an auxiliary connection between the forced and natural circulation systems outside of the furnace chamber and communicating with the manifold at the cold water inlet.

5. For use in a boiler structure, a generally elongated drum adapted to be used as an upper drum, a lateral bafile structure intermediate the ends of the drum dividing it into two portions, the baflle structure including a screening medium below the normal water level in the drum, a plurality of openings in one portion spaced longitudinally along both sides of the drum and converging toward the bottom, said openings being adapted for the connection of circulation tubes, longitudinal baffle struc ture depending from the side walls of the drum and masking the openings, said structure including a screening medium below the normal water level, an auxiliary steam outlet in the said one portion of the drum, and a hot water outlet in the other.

6. The structure of claim 5 wherein the lateral and longitudinal bafile structures are joined together.

7. For use in a boiler structure, an elongated drum adapted to be used as an upper drum, a lateral battle structure intermediate the ends of the drum dividing it into two portions, the baffie structure including a screening medium below the normal water level in the drum, a plurality of openings in one portion spaced longitudinally along both sides of the drum and converging 6 toward the bottom, said openings being adapted for the connection of circulation tubes, longitudinal baffle structure depending from the side walls of the drum and masking the openings, said structure including a screening medium below the normal water level, and hot water and auxiliary steam outlets for the drum.

8. In a boiler unit for generating hot water and steam, a boiler structure including a housing, a water and steam circulation system for the housing including an upper drum and lower drum means having two lower chambers, the housing being divided generally laterally into a forward furnace chamber and a rear hot gas path, the system including a forced circulation system having a cold water inlet connected to one of the lower drum chambers, water wall tubes around the front end of the chamber connected to one lower drum chamber and the upper drum, a natural circulation system including convection tubes extending through the gas path connected to the upper drum and the other lower drum chamber, an auxiliary connection between the forced and natural circulation systems including at least one open pipe communicating with the one lower drum chamber and the natural circulation system which is outside of the furnace chamber, a lateral battle structure in the upper drum dividing it into two portions conforming generally to the furnace chamber and gas path, a hot Water outlet in the portion of the upper drum corresponding to the gas path, the auxiliary connection communicating with the upper drum in the portion corresponding to the gas path and adjacent the hot water outlet, and an additional baffle structure in the portion of the upper drum corresponding to the gas path adjacent and disposed at least in part effectively between the point of communication of the auxiliary connection and the hot water outlet so that the relatively cold water discharged from the auxiliary connection is diverted and effectively mixed with the hot water in the drum before it can be discharged through the hot water outlet.

9. The structure of claim 8 further characterized in that the one lower drum chamber includes a rectangular manifold around the forward furnace chamber connected to the cold water inlet, the auxiliary connection being connected directly to the manifold.

10. The structure of claim 8 further characterized by and including an auxiliary steam outlet in the other portion of the upper drum corresponding to the furnace chamber.

References Cited in the file of this patent UNITED STATES PATENTS 850,358 Elliott Apr. 16, 1907 1,927,095 Lucke Sept. 19, 1933 2,256,576 Rehm Sept. 23, 1941 2,283,201 Gillette et al. May 19, 1942 2,435,055 Rehm Jan. 27, 1948 

